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><H1
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><A
NAME="AEN542"
>4.5. The <TT
CLASS="FILENAME"
>/usr</TT
> filesystem</A
></H1
><P
>The <TT
CLASS="FILENAME"
>/usr</TT
> filesystem is often
	large, since all programs are installed there.	All files
	in <TT
CLASS="FILENAME"
>/usr</TT
> usually come from a Linux
	distribution; locally installed programs and other stuff goes
	below <TT
CLASS="FILENAME"
>/usr/local</TT
>.	This makes it possible
	to update the system from a new version of the distribution,
	or even a completely new distribution, without having to
	install all programs again.  Some of the subdirectories of
	<TT
CLASS="FILENAME"
>/usr</TT
> are listed below (some of the less
	important directories have been dropped; see the FSSTND for
	more information).

	<DIV
CLASS="GLOSSLIST"
><DL
><DT
><B
><TT
CLASS="FILENAME"
>/usr/X11R6</TT
></B
></DT
><DD
><P
>The X Window System, all files. To simplify
		the development and installation of X, the X files have not
		been integrated into the rest of the system.  There is a
		directory tree below <TT
CLASS="FILENAME"
>/usr/X11R6</TT
> similar
		to that below <TT
CLASS="FILENAME"
>/usr</TT
> itself.
		</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/usr/bin</TT
></B
></DT
><DD
><P
>Almost all user commands. Some commands are
		in <TT
CLASS="FILENAME"
>/bin</TT
> or in
		<TT
CLASS="FILENAME"
>/usr/local/bin</TT
>.
		</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/usr/sbin</TT
></B
></DT
><DD
><P
>System administration commands that are not
		needed on the root filesystem, e.g., most server programs.
		</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/usr/share/man</TT
>, 
<TT
CLASS="FILENAME"
>/usr/share/info</TT
>, 
<TT
CLASS="FILENAME"
>/usr/share/doc</TT
></B
></DT
><DD
><P
>Manual pages, GNU Info documents, and
		miscellaneous other documentation files, respectively.
		</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/usr/include</TT
></B
></DT
><DD
><P
>Header files for the C
		programming language.  This should actually be below
		<TT
CLASS="FILENAME"
>/usr/lib</TT
> for consistency, but the
		tradition is overwhelmingly in support for this name.
		</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/usr/lib</TT
></B
></DT
><DD
><P
>Unchanging data files for programs and
		subsystems, including some site-wide configuration
		files.	The name <TT
CLASS="FILENAME"
>lib</TT
> comes from library;
		originally libraries of programming subroutines
		were stored in <TT
CLASS="FILENAME"
>/usr/lib</TT
>.
		</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/usr/local</TT
></B
></DT
><DD
><P
>The place for locally installed software and
		other files.  Distributions may not install anything in
		here.  It is reserved solely for the use of the local
		administrator.  This way he can be absolutely certain that
		no updates or upgrades to his distribution will overwrite
		any extra software he has installed
		locally.</P
></DD
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>The <TT
CLASS="FILENAME"
>/dev</TT
> directory</TD
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